EP1664896B1 - Electrically rotatable micromirror or microlens - Google Patents

Abstract

The micro-mirror has a movable part (10) with reflecting zone and an electric control unit comprising two actuators (19). Each has a fixed electrode connected to a fixed part (14). A movable electrode (21) has a free end (21.1) and an end connected to a drive arm (23). The movable electrode is plated on the fixed electrode from the free end, when actuating voltage is applied between the electrodes. An independent claim is also included for a method of manufacturing a micro mirror.

Description

TECHNICAL AREA

The present invention relates to a micro-mirror or a micro-lens operable electrically in rotation. Micro-mirrors and micro-lenses resulting from micromachining techniques of semiconductor material are of great interest for the reflection or the transmission of a light beam thanks to the combination of their speed, their precision, their low energy consumption and their relatively low cost.

Such micro-mirrors or microlenses can operate in two different modes which are the static or quasi-static mode and the oscillating mode. The micro-mirrors comprise a movable part, generally in the form of a plateau, provided with a reflecting zone. The microlenses comprise a perforated mobile part (that is to say in the form of a frame) on which is fixed a refracting lenticular piece forming a refractive zone.

In the first mode, the moving part can take positions in which it is inclined at a fixed angle with respect to a rest position or it can move in rotation, its movement having a very small frequency in front of its resonant frequency. In this first mode, the reflected or transmitted light beam according to whether it is a micro-mirror or a micro-lens is pointed towards a user device and the field of application is, for example, optical routing systems or image projection systems.

In the second mode of operation, the mobile part oscillates at its resonance frequency, the reflected or transmitted light beam performs a periodic scan with an amplitude increased by the mechanical resonance phenomenon. The field of application is, for example, scanners in printers or barcode readers. In this mode of operation, the micro-mirrors can also be used in new applications such as the light beam scanning displays on the retina or the endoscopic confocal microscopes.

STATE OF THE PRIOR ART

Such micro-mirrors or microlenses conventionally comprise a mobile part, generally in the form of a plateau, provided with a main plane and having at least one reflecting zone for the micro-mirror and a refractive zone for the micro-lens, a fixed part, connecting means of the movable part to the fixed part embodying an axis substantially parallel to the main plane, electrical control means of the rotation of the movable portion about the axis.

The optical quality of the micro-mirrors depends essentially on the flatness of their reflecting zone. That of microlenses depends on the precision of the shape of the lens, shape close to a sphere for example.

The mobile part of the micro-mirrors generally comprises a micro-machined plate of semiconductor material forming the reflective zone or covered with at least one reflective layer and optionally a protective layer. For microlenses, the mobile part comprises a perforated plate supporting a lenticular refracting piece. The surface deformations may be induced by elements lying under the reflective zone or under the perforated plate supporting the lenticular piece. These elements, like electrodes, are very often used to generate the displacement of the mobile part, the stresses in the surface layer or layers of the mobile part (for example the reflective metal layer or the protective layer) and the dynamic deformations which occur during moving of the moving part.

The use of monocrystalline silicon with a thickness of a few tens of micrometers makes it possible to obtain moving parts having a satisfactory flatness. Such a range of thicknesses makes it possible to avoid the deformations generated by an acceleration during a movement or by the stresses provided by the surface layer or layers.

The size of the reflective zone must be sufficient to limit the diffraction effect of the light beam on its opening. Micro-mirrors typically larger than 500 micrometers are typically used. Of course such dimensions are not limiting, they actually depend on the application. These dimensional constraints are applicable to micro-lenses.

These micromirrors or microlenses are therefore intended to move in rotation about an axis substantially parallel to their main plane. Two or more micro-mirrors can be used in the same assembly to deflect the light beam several times. The same remarks apply to micro-lenses.

Micro-mirrors actuated in rotation by electrostatic effect are known as that illustrated in FIGS. 1A, 1B. The moving part 1 is mounted on an axis of rotation 2 embodied by two aligned torsion arms 3 coming from the mobile part 1 and whose ends are secured to a fixed part 4. The movable part 1 faces the fixed part 4 while being at a distance in the rest position, it is represented by the dotted lines in FIG. 1A. It is suspended above the fixed part 4 by the torsion arms 3. Electric control means 5 for rotating the movable part 1 are provided. They comprise a mobile electrode 5.1 and two fixed counter-electrodes 5.2. The face of the moving part 1 which faces the fixed part 4 carries the moving electrode 5.1. The other face of the moving part 1 carries a reflecting zone 7. The fixed part 4 carries the two counter electrodes 5.2, 5.2 which face the moving electrode 5.1. The means 5 for controlling the rotational movement of the mobile part 1 also comprise means 5.4 of addressing (materialized by voltage sources) for applying an addressing signal in the form of an actuating voltage V1 or V2 between the moving electrode 5.1 and one or the other of the counter-electrodes 5.2 , 5.3. When applying such an actuating voltage V1 or V2, an electrostatic attraction force F (x) is generated and the moving part 1 moves in rotation about the axis 2, the moving electrode 5.1 being attracted by the counter electrode 5.2 or 5.3 which generated the potential difference V1 or V2.

A problem posed by the electrostatic actuation is that the elastic restoring force (not shown), caused by the torsion arms 3, which opposes the displacement of the moving part is linear whereas the electrostatic attraction force is quadratic. . In addition, when the moving part 1 has traveled about a third of the distance separating, at rest, the moving electrode 5.1 from the counter-electrode 5.2 or 5.3, the attraction force takes over and a phenomenon of abrupt plating of the electrodes when the potential difference exceeds a certain threshold Vc or pull-in voltage (literally threshold voltage of attraction). Before the potential difference reaches the pull-in voltage, the response of the moving part (ie the angle of rotation as a function of the voltage) is not linear, which complicates the control .

As a result, the controlled travel of the moving electrode corresponds to a distance that is largely restricted with respect to the initial distance separating the moving electrode 5.1 of the counter-electrodes 5.2, 5.3 in the rest position. This phenomenon limits the usable deflection of the moving part 1. A small space at rest between the moving electrode and the counter-electrodes will only allow a mobility with a very small angle, and the installation of a larger space at rest would involve the use of a very large actuating voltage, which is undesirable. In addition, the movement of the moving part is relatively limited.

The document [1], whose references are at the end of the description, shows another embodiment of a rotating micromirror capable of moving in a single direction during the attraction between two electrodes. This embodiment is illustrated in Figures 2A, 2B. The micro-mirror has substantially the same structure as before with a fixed part 4, a mobile part 1 located at rest at a distance from the fixed part 4, provided with a reflecting zone 7 and an axis of rotation 2 materialized by two torsion arm 3 whose ends are integral with the fixed part 4 and which come from the moving part 1. The difference with the previous example is at the level of the electrical control means 5 of the rotation of the movable part 1. The electrical control means 5 comprise a mobile electrode 50 issuing from the mobile part 1 and having a free end 50.1 and a fixed electrode 51 carried by the fixed part 4, opposite the mobile electrode 50 in the rest position. The movable electrode 50 is secured to an edge of the mobile part 1. The electrical control means 5 also include addressing means for applying an addressing signal in the form of an actuating voltage between the fixed electrode 51 and the moving electrode 50. These means are not shown so as not to overload the figures. The movable electrode 50 is relatively flexible, it is intended to be pressed gradually from its free end 50.1 on the fixed electrode 51. The movable electrode 50 is oriented substantially perpendicular to the axis of rotation 2. The Progressive plating phenomenon between the movable electrode 50 and the fixed electrode 51 is known by the name of "zipping effect". An electrically insulating layer (not visible in the figures) is generally interposed between the fixed electrode 51 and the moving electrode 50 to prevent the appearance of short circuits. The movable electrode 50 generally comprises a body 50.2 which ends with a primer 50.3 at its free end 50.1. The width of the primer 50.3 is greater than the width of the body 50.2 of the moving electrode 50.

At rest the fixed electrode 51 and the movable electrode 50 are distant from each other. When the addressing means apply an addressing signal, namely an actuating voltage between the moving electrode 50 and the fixed electrode 51, as long as this voltage is lower than the threshold voltage Vc, the electrode mobile 50 begins to approach the fixed electrode 51. When the actuation voltage reaches the value Vc, a portion of the movable electrode 50 substantially corresponding to the primer 50.3 is reached. to stick on the fixed electrode 51. The movable portion 1 inclines at an angle θ relative to the position it had at rest before the application of the actuating voltage. This angle is greater than a minimum angle θmin whose meaning will be given later. The greater the actuation voltage increases between the two electrodes 50, 51 the longer the length of the moving electrode 50 is applied to the fixed electrode 51, the more the moving part 1 of the micro-mirror moves in rotation around the axis. 2. The angle of inclination θ of the movable part 1 and therefore of the reflecting zone 7 is substantially proportional to the actuation voltage applied between the fixed electrode 51 and the moving electrode 50. When the actuating voltage decreases, the part mobile 1 adopts the same behavior as before but in the opposite direction until the actuation voltage reaches a minimum value Vd (pull-out voltage or threshold separation voltage) to maintain the end 50.1 of the mobile electrode 50 just plated on the fixed electrode 51. This voltage Vd is lower than the voltage Vc. When this voltage is applied, the mobile part 1 is inclined at the angle θmin. When the operating voltage decreases below Vd, the movable electrode 50 is detached from the fixed electrode 51 and the movable portion 1 resumes its substantially horizontal rest position. FIG. 2C represents the response curve (rotation angle θ as a function of the operating voltage V applied between the fixed electrode 51 and the moving electrode 50) of such a micro-mirror.

Compared to the previous example with conventional electrostatic actuation, the actuating voltage can be reduced for the same angle of rotation. There is good linearity between the operating voltage and the inclination angle of the moving part, which makes it easy to obtain a precise orientation of the moving part. The force developed by the displacement of the moving part is inversely proportional to the square of the distance separating the moving electrode from the fixed electrode. But this distance is very small in the vicinity of the plated part of the moving electrode. This force is therefore very important in the range of use of the micro-mirror. This distance is at least equal to the thickness of the dielectric layer covering the fixed electrode. It is thus possible to rotate the moving part with angles of the order of 10 degrees with a moderate voltage typically less than about 100 V. In the rest position, the moving electrode must not be too far from the electrode fixed (a few micrometers to a few tens of micrometers) to limit the operating voltage, because the electrostatic force generated during the application of the operating voltage decreases rapidly when the distance between the two electrodes increases. A first disadvantage of such a device is that the moving part can not move in rotation on either side of the movable part. Another disadvantage of this type of actuation is that the moving part can not take certain orientations, these orientations correspond to angles θ strictly included between 0 and θmin.

It can be seen in FIGS. 2A, 2B that the axis of rotation 2 is offset with respect to the geometrical center of the mobile part 1. The offset is made so as to bring it closer to the moving electrode 50. This feature makes it possible to increase the travel of the movable part 1 while pushing the moment when it comes into abutment with the fixed part 4 which supports the fixed electrode 51. But, even with this feature, the movable part 1 always has a limited movement. There is a tendency to reduce the size of the moving part 1, but it is necessary to find a compromise between movement and size of the reflecting zone 7, the latter must have a size appropriate to the optical function that it must fulfill. It is often desirable for the reflecting zone 7 to have a span of between a few hundred micrometers and a few millimeters. The same compromise is to be found for the size of the refractive zone of the micro-lens. Another disadvantage of this configuration is that there is a risk of introducing a vertical component to the movement of the center of the reflecting zone 7, which can give a lateral translational movement to a reflected light beam resulting from a light beam. incident at this location.

Additional information on the micro-mirrors using "zipping" actuating means can be found in document [2], the references of which are also specified at the end of the description. In this document, control means are intended to deform the micromirror and not to move it in rotation.

It is also known from document [3], the references of which are mentioned at the end of the description, a micro-mirror whose electrical control means for the rotation comprise several pairs of interdigital electrodes 7.1, 7.2 in the form of combs. In one pair of electrodes, one of the comb electrodes 7.2 is secured to the fixed part 4. The other electrode 7.1 is secured via a hinge 8.1 of an arm 8 which is derived from the mobile part 1. This arm 8 is parallel to the torsion arm 3 secured to the fixed part 4 which contributes to materialize the axis of rotation. This type of actuation is very effective in the oscillating mode, thanks to the phenomenon of mechanical resonance, but is not well suited to operate in the static or quasi-static mode. In the static or quasi-static mode, this type of actuation is more efficient than the conventional electrostatic actuation but remains insufficient to obtain large angles of rotation.

The fact that the movable interdigital electrode is integral with an arm 8 which is not the torsion arm has the disadvantage of moving the interdigitated electrode away from the axis of rotation and thus reducing the maximum deflection for an actuation voltage given.

EP 1 193 528 and US 6,115,231 show a micro-mirror and a micro-relay, respectively, comprising a fixed electrode and a moving electrode.

STATEMENT OF THE INVENTION

The object of the present invention is to propose a micro-mirror or a micro-lens capable of taking one or more static or quasi-static rotational positions that do not have the above limitations and difficulties. These limitations also applied to micro-lenses.

More specifically, an object of the invention is to provide a micro-mirror or a micro-lens capable of moving in rotation with a large amplitude and which can take a precise fixed position while maintaining a reduced actuation voltage.

Another object of the invention is to provide a micro-mirror or a micro-lens which can take an angle of inclination in a wide range of angles, this range being continuous and extending on both sides its rest position corresponding to a zero inclination angle.

Another object of the invention is to provide a micro-mirror or a micro-lens capable of taking a position which is not likely to introduce a vertical component to the movement of the central part of the reflecting zone of the micro-mirror or the refractive zone of the micro-lens, this central zone being generally that on which a light beam is reflected or transmitted.

Another object of the invention is to provide a micro-mirror or a micro-lens whose movable portion is larger than in conventional micro-mirrors or microlenses.

To achieve this, the present invention provides a micro-mirror or a micro-lens comprising a movable part with a reflective zone or a refractive zone respectively, a fixed part, means for connecting the moving part to the fixed part showing an axis of rotation contained in the movable portion, substantially parallel to a main plane of the movable portion, and electrical control means of the rotation of the movable portion about the axis. According to the invention, the electrical control means comprise two or more actuators, each formed of a fixed electrode integral with the fixed part and of a mobile electrode provided with a free end and an end connected to an arm. drive substantially parallel to the axis and issuing from the moving part, the mobile electrode being adapted to progressively tap on the fixed electrode from its free end when an actuating voltage is applied between the two electrodes of one of the actuators, the plating being done on a variable surface depending on the voltage applied between the electrodes of the actuator, the actuators being disposed on either side of the axis.

Thus the moving part can move in rotation with a maximum amplitude double that existing in the configuration described in document [1]. An amplitude greater than about plus or minus 10 degrees can be obtained, more than 20 degrees total.

The connecting means of the mobile part to the fixed part may be two torsion arms from of the movable part whose ends are connected to the fixed part.

Advantageously, the axis can pass through the geometric center of the moving part, which avoids introducing a vertical component to the movement of the central zone of the movable part.

It is possible that on the same side of the moving part, a driving arm is offset relative to a torsion arm. But it is particularly advantageous to increase the travel that a torsion arm and a drive arm are in the extension of one another.

In this latter configuration, to maintain both torsional and vertical flexural stiffness, it is preferable that at least one torsion arm has a cross section smaller than that of a drive arm.

It is of course possible that a torsion arm and a drive arm located in the extension of one another have substantially the same cross section, the two arms are then merged.

In a particularly effective embodiment, several mobile electrodes can be connected to the same drive arm.

In another embodiment, each drive arm may be integral with a single movable electrode.

In yet another embodiment that improves the accuracy of the position taken by the mobile part, several mobile electrodes located on the same side of the axis are connected to each other at their free end.

To make the micro-mirror or the micro-lens more compact, it is possible for a moving electrode to be wound on itself, its free end being in a central zone of the winding.

A rectilinear moving electrode configuration is also possible.

A movable electrode configuration which makes it possible to reduce the voltage necessary to obtain the plating of the moving electrode on the fixed electrode of an actuator is that the moving electrode comprises a body of substantially constant width extending by a primer at level of its free end, the width of the primer being greater than that of the body.

It is possible that the fixed electrodes are merged, which facilitates the realization, in this configuration the addressing is done by the mobile electrodes.

The fixed part may comprise a base and amounts on which support the connecting means of the movable part to the fixed part, the movable part being suspended above the base.

To increase the movement of the movable portion, the base may comprise a recess facing the movable portion which is then suspended above the recess.

To avoid short circuits between the electrodes of the actuators, the fixed electrodes can be covered with a dielectric material.

The control means may comprise addressing means capable of applying an actuating voltage to the moving electrodes and / or to the fixed electrodes of an actuator.

The operating voltage may be a DC voltage superimposed on a variable control voltage.

To simplify the control of the rotation, it is possible for at least one fixed electrode of an actuator to be split up into two portions, one end portion of which, these two portions being isolated from one another, the means of addressing being able to apply a DC voltage to the end portion and a variable control voltage to the other portion.

The DC voltage may be a minimum voltage to maintain a plating of the free end of the moving electrode of the actuator on the fixed electrode.

When the control voltage applied to an actuator on one side of the axis is non-zero, the control voltage applied at the same time to an actuator located on the other side of the axis may be zero.

1. a) gravure du contour d'une première région de la partie mobile, d'une première région de la partie fixe, d'une première région des moyens de liaison de la partie mobile à la partie fixe, d'une première région des bras d'entraînement dans une couche superficielle et une première couche isolante d'un substrat stratifié comportant un empilement alterné d'une première et une seconde couches en matériau isolant et de deux couches semi-conductrices dont une est intermédiaire et l'autre superficielle,
2. b) dans un second substrat semi-conducteur gravure d'une partie en retrait, ce second substrat contribuant à réaliser une seconde région de la partie fixe et les électrodes fixes des actionneurs,
3. c) assemblage des deux substrats, la partie en retrait étant face à la couche superficielle gravée,
4. d) gravure du contour des électrodes mobiles, d'une seconde région de la partie mobile, d'une seconde région des bras d'entraînement et d'une seconde région des moyens de liaison, dans la couche intermédiaire et réalisation au préalable de métallisations reliées électriquement aux électrodes mobiles pour l'application de la tension d'actionnement de chaque actionneur via la partie fixe et la partie mobile.

The present invention also relates to a method for producing a micro-mirror or a micro-lens thus characterized. It comprises the following steps:

1. a) etching the contour of a first region of the moving part, a first region of the fixed part, a first region of the connecting means of the moving part to the fixed part, a first region of the arms driving in a surface layer and a first insulating layer of a laminated substrate comprising an alternating stack of a first and a second layer of insulating material and of two semiconductor layers, one of which is intermediate and the other superficial,
2. b) in a second semiconductor substrate etching a recessed part, this second substrate contributing to producing a second region of the fixed part and the fixed electrodes of the actuators,
3. c) assembling the two substrates, the recessed part facing the etched surface layer,
4. d) etching the contour of the moving electrodes, a second region of the movable part, a second region of the drive arms and a second region of the connecting means, in the intermediate layer and prior realization of metallizations electrically connected to the moving electrodes for applying the actuating voltage of each actuator via the fixed part and the movable part.

According to this method, isolation trenches can be made in step a) in the superficial layer and in the upper insulating layer at the first region of the fixed part and the first region of the moving part. and in the intermediate layer during step d) at the level of movable electrodes and the second region of the movable portion for electrically isolating the moving electrodes upon application of the actuating voltage to a moving electrode via the first region of the fixed portion and the first region of the movable portion .

Step b) may include etching the recess in a central portion of the recessed portion.

Step b) may be followed by a step of producing a layer of insulating material on the second etched substrate.

The second region of the moving part can directly make the reflecting zone of the micro-mirror or a metallization step of the second region of the moving part can be provided to realize the reflecting zone of the micro-mirror.

With regard to the micro-lens, it is possible to engrave the mobile part in the form of a frame during step b).

It is possible to assemble a lenticular refracting part in the frame of the movable part to produce the refractive zone.

After assembly of step c), the second insulating layer may be removed.

The thickness of the superficial layer is chosen to be greater than the intermediate layer so as to obtain suitable torsion characteristics for the torsion arms.

The first substrate may advantageously be a double SOI substrate and comprise next to the second insulating layer is a base semiconductor layer which is removed after the two substrates have been assembled.

BRIEF DESCRIPTION OF THE DRAWINGS

• Les figures 1A, 1B (déjà décrites) montrent une vue en coupe et une vue en trois dimensions d'un micro-miroir de l'art antérieur actionnable en rotation de manière électrostatique ;
• Les figures 2A, 2B (déjà décrites) montrent une vue en trois dimensions' et une vue de dessus d'un micro-miroir de l'art antérieur actionnable en rotation par effet « zipping » et la figure 2C illustre l'angle d'inclinaison de la partie mobile du micro-miroir en fonction de la tension appliquée ;
• La figure 3 (déjà décrite) est une vue de dessus d'un micro-miroir actionnable en rotation à l'aide d'électrodes interdigitées en peigne ;
• La figure 4 est une vue de dessus d'un exemple de micro-miroir ou de micro-lentille selon l'invention
• Les figures 5A, 5B illustrent une vue de dessus et une vue en coupe d'un autre exemple de micro-miroir ou de micro-lentille selon l'invention ;
• Les figures 6A, 6B sont des coupes du micro-miroir ou de la micro-lentille des figures 5, destinées à expliquer un premier mode de fonctionnement, et la figure 6C représente la variation de l'angle d'inclinaison de la partie mobile du micro-miroir ou de la micro-lentille en fonction de la tension appliquée dans ce mode de fonctionnement ;
• La figure 7 est une coupe du micro-miroir ou de la micro-lentille des figures 5 destinée à expliquer un second mode de fonctionnement ;
• La figure 8A est une coupe du micro-miroir ou de la micro-lentille des figures 5 destinée à expliquer une variante du second mode de fonctionnement et la figure 8B représente la variation de l'angle d'inclinaison de la partie mobile du micro-miroir ou de la micro-lentille en fonction de la tension appliquée dans ce mode de fonctionnement ;
• La figure 9 est une vue de dessus partielle d'un autre exemple de micro-miroir selon l'invention avec des électrodes mobiles-enroulées ;
• La figure 10 est une vue de dessus partielle d'un autre exemple de micro-miroir selon l'invention dans lequel les extrémités libres des électrodes mobiles des actionneurs situés d'un même côté de l'axe sont communes ;
• Les figures 11A à 11L représentent des étapes d'un exemple de procédé de réalisation de micro-miroirs ou de micro-lentilles selon l'invention.

The present invention will be better understood on reading the description of exemplary embodiments given, purely by way of indication and in no way limiting, with reference to the appended drawings in which:

• FIGS. 1A, 1B (already described) show a sectional view and a three-dimensional view of a micro-mirror of the prior art that can be electrostatically rotated;
• FIGS. 2A, 2B (already described) show a three-dimensional view and a view from above of a micro-mirror of the prior art operable in rotation by "zipping" effect and FIG. 2C illustrates the angle of inclination of the moving part of the micro-mirror as a function of the applied voltage;
• Figure 3 (already described) is a top view of a micro-mirror operable in rotation using interdigitated comb electrodes;
• FIG. 4 is a view from above of an example of a micro-mirror or a micro-lens according to the invention
• Figures 5A, 5B illustrate a top view and a sectional view of another example of micro-mirror or micro-lens according to the invention;
• FIGS. 6A, 6B are sections of the micro-mirror or micro-lens of FIG. 5, intended to explain a first mode of operation, and FIG. 6C represents the variation of the inclination angle of the moving part of the micro-mirror or the micro-lens as a function of the voltage applied in this mode of operation;
• Figure 7 is a sectional view of the micro-mirror or micro-lens of Figures 5 for explaining a second mode of operation;
• FIG. 8A is a sectional view of the micro-mirror or micro-lens of FIGS. 5 to explain a variant of the second mode of operation, and FIG. 8B shows the variation of the angle of inclination of the mobile part of the micro-mirror. mirror or micro-lens depending on the voltage applied in this mode of operation;
• Figure 9 is a partial top view of another example of a micro-mirror according to the invention with mobile-wound electrodes;
• FIG. 10 is a fragmentary top view of another example of a micro-mirror according to the invention in which the free ends of the moving electrodes of the actuators located on the same side of the axis are common;
• FIGS. 11A to 11L show steps of an exemplary method for producing micro-mirrors or microlenses according to the invention.

The different variants must be understood as not being exclusive of each other.

Identical, similar or equivalent parts of the different figures bear the same numerical references to facilitate the transition from one figure to another.

The different parts shown in the figures are not necessarily in a uniform scale, to make the figures more readable.

DETAILED PRESENTATION OF PARTICULAR EMBODIMENTS

Reference will now be made to FIGS. 4, 5A, 5B which show examples of micro-mirror or micro-lens according to the invention. The micro-mirror or the micro-lens comprises a movable portion 10 and a fixed portion 14. The movable portion 10 generally takes the form of a plate or a frame respectively. It is intended to be rotated about an axis 12. The axis passes through the movable portion 10 and is substantially parallel to a main plane of the movable portion 10. Connecting means 13 of the movable portion 10 to the fixed part 14 materialize this axis 12. These connecting means can take the form of two torsion arms 13 from the movable portion 10 and which have an end 11 secured (for example by embedding) of the fixed portion 14 at uprights 15 The two torsion arms 13 are in the extension of one another. The uprights 15 of the fixed part 14 rest on a base 16 which extends under the moving part 10. The mobile part 10 is thus suspended above the fixed part 14 at its base 16. The movable part 10 comprises main faces, one of which is turned towards the fixed part 14 at its base 16 and the other end of which has a reflecting zone 17 (hatched in Figure 4) for reflecting light in the case of a micro-mirror. The reflective zone 17 is shown as occupying only partially the face of the moving part 10 but it could occupy it completely. In the case of a micro-lens, the zone 17 represents a refractive zone, it may be a lenticular refracting piece fixed, for example by gluing, to the frame 10. The axis 12 may pass through the geometric center of the movable part 10.

The micro-mirror or the micro-lens also comprises electric control means 18 for the rotational displacement of the mobile part 10. These means 18 comprise at least two actuators 19 with "zipping effect" and addressing means (not visible in Figure 4) of these actuators.

By actuator 19 "zipping effect" means an actuator formed of a pair of electrodes 20, 21 with a fixed electrode 20 and a movable electrode 21 having a free end 21.1, the movable electrode 21 being intended to come to press on the fixed electrode 20 from its free end 21.1, the plating being done on a variable surface according to a voltage applied between the two electrodes. The moving electrode 21 is therefore flexible.

The fixed electrode 20 of the actuators 19 is secured to the fixed portion 14 at the base 16. It is not visible in Figure 4, it is hidden by the movable electrode 21. It is visible in Figure 5B . The movable electrode 21 of the actuators 19 is secured at its other end to an arm drive 23 which is derived from the movable portion 10 and which is directed substantially parallel to the axis of rotation 12. This drive arm 23 is sufficiently rigid. Thus the movable electrode 21 is no longer directly attached to the movable portion 10 as in the examples of Figures 2, it is shifted.

According to an important characteristic, the free ends 21.1 of the movable electrodes 21 of the two actuators 19 are located on either side of the axis of rotation 12. The actuators 19 are therefore arranged on either side of the axis 12 Thus, each of the actuators 19 can drive the moving part 10 in one direction or the other, which makes it possible to increase its travel compared with the example of FIGS. else of the rest position (zero angle) can be obtained with an operating voltage typically less than 100V.

The actuators 19 can be addressed or actuated either separately or simultaneously as will be seen later.

The movable portion 10 may have a span between a few hundred micrometers and a few millimeters and a thickness of about a few tens of micrometers. It must have sufficient rigidity so that the reflecting or refracting zone 17 that it carries remains as stable as possible so as to maintain its optical quality whatever the conditions and especially during acceleration. These dimensions are not limiting of course.

The movable electrode 21 may take the form from the drive arm 23, a substantially rectilinear body 21.2 of substantially constant width terminating at its free end 21.1 by an end portion 21.3 which may be of the same width that the body 21.2 or advantageously that can be wider. In the latter case the end portion 21.3 can be qualified as a primer. This primer 21.3 is visible in FIG. 5A. As for the fixed electrode 20, it can have any shape insofar as the mobile electrode 21 can be pressed on it.

The primer 21.3 serves to reduce the threshold voltage of attraction Vc as well as the cutoff threshold voltage Vd.

When the actuator is at rest, it is not subjected to any actuating voltage. Its mobile and fixed electrodes 20, 21 are separated by a space 25 which can be full of a gas (air or other) or which can be empty. This inter-electrode gap 25 is illustrated in FIG. 5B. This space 25 may be delimited by a cavity that contribute to form the amounts in the form of a frame as will be seen later.

It is preferable to place in this space 25 a layer of dielectric material 24 interposed between the fixed electrodes 20 and the moving electrodes 21 to avoid a short circuit when a movable electrode 21 comes into contact with a fixed electrode 20. This dielectric layer 24 is visible in FIG. 5B, it covers the fixed electrodes 20. The thickness of the dielectric layer 24 is between a minimum value and a maximum value. The minimum value is determined by the breakdown of the insulator subjected to an electric field generated by a given actuation voltage applied between the two electrodes of an actuator. The maximum value is determined by the maximum distance by which the two electrodes of an actuator can be located when the moving part 10 is in the rest position without the attraction force being too low for a given actuating voltage . For example, for an actuating voltage of 100 V, the minimum thickness of the dielectric layer 24 (made for example of oxide or nitride of a semiconductor material, silicon for example) will be about 0.2 micrometer .

As an indication, the movable electrode 21 may have a length of between a few tens of micrometers and a few millimeters, a thickness of between a few tenths of micrometers and a few micrometers, and a body width 21.2 much greater than its thickness. The thickness makes the movable electrode 21 sufficiently flexible in a direction substantially perpendicular to the surface of the base 16. If there is a primer 21.3, the latter is larger than the width of the body 21.2. At rest, the inter-electrode gap may be from a few micrometers to a few tens of micrometers.

It is advantageous that the base 16 comprises facing the mobile part 10 a recess 26. The movable portion 10 is able to enter the recess 26 when the movable portion 10 takes a sloped position with a large angle. The taking of an inclined position with such an angle of inclination would not be possible in the absence of the recess 26 because the movable portion 10 would hit the base 16. The fixed electrodes 20 are located on the base 16 to the outside of the recess 26 so as to maintain the relatively low inter-electrode space 25 in the rest position of the actuators. The depth of the recess is chosen to be sufficient for the mobile part to be inclined at an angle θmax without striking the base 16. The angle θmax corresponds to the maximum angle taken by the moving part when the addressing means (described later) deliver a maximum operating voltage.

The recess 26 may be a hole through the base 16 or only a blind hole in the base 16. If it is a through hole, it may be made from the face of the base 16 intended to receive the fixed electrodes 20 (this face is said front face) or from the other face of the base 16 which is called back face. This recess 26 will rather be achieved by wet etching than dry etching in the material of the base 16 which is generally a semiconductor material.

The distance d between the axis of rotation 12 and the fixed part 14 at the level of the plating surface must be relatively large (for example greater than about 50 micrometers) if it is desired to large inclination angle (eg greater than 5 °).

It is possible that the uprights supporting the torsion arms 13 take the form of a frame 15.1 which surrounds the mobile part 10 and the actuators 19 and which is integral with the base 16. This variant is shown in Figures 5A and 5B. This frame 15.1 can contribute to delimiting a cavity. It is preferred to limit the area occupied by this cavity so as to facilitate a step of sealing two substrates, which will be described later in the description of an exemplary method for producing a micro-mirror or a micro-lens. according to the invention.

The driving arms 23 may be distinct from the torsion arms 13 as in FIG. 4. In this configuration, a torsion arm and a driving arm situated on one and the same side of the movable part are offset relative to one another. to the other. This is not of course an obligation as illustrated in Figure 5A. In this figure, the drive arm 23 is closer to the movable portion 10 than is the torsion arm 13 which extends it. Subsequently, unless otherwise indicated, it is considered that a drive arm 23 and a torsion arm 13 are in the extension of one another.

It is preferable that the connection of the movable electrodes 21 to the drive arms 23 is as close as possible to the axis of rotation 12 so as to allow a large clearance of the movable portion 10 while maintaining the inter-electrode space Actuators 19 relatively low.

The actuators 19 can be located on either side of the movable part 10, but this is not an obligation, one could consider having only one pair of actuators 19 with the actuators 19 located on the same side of the movable part 10. Referring to FIG. 5A, only two of the four actuators shown could be represented, for example those corresponding to the section of FIG. 5B.

In FIGS. 6A, 6B and following, the torsion arms 13 are in the extension of the driving arms 23. In practice, a torsion arm 13 has a cross section smaller than that of a driving arm 23; cross section gives it some flexibility in torsion. The drive arm 23 has a larger cross section to remain rigid during training.

Thus, the dimensioning of the torsion arms 13 can be optimized so that they are sufficiently flexible in torsion and sufficiently stiff in vertical flexion. They are advantageously relatively thick and their width will be less than their thickness. If the torsion arm 13 is not rigid enough in vertical bending, the actuator 19 will tend to pull the movable portion 10 down rather than rotate it. The movement of the mobile part 10 may then not be a pure rotation, which can give a lateral translational movement to a reflected or transmitted light beam resulting from an incident light beam on the reflective or refractive zone 17.

We will now give explanations on the operation of such a micro-mirror or such a micro-lens operable in rotation about an axis.

Referring to Figs. 6A, 6B and the graph of Fig. 6C. It is assumed that in this first mode of operation, the actuators 19 located on either side of the axis 12 are actuated separately. Addressing means 27 actuate either one or more actuators located on one side of the axis 12, or one or more actuators located on the other side of the axis 19.

At rest the mobile part 10 is in a substantially horizontal position (inclination angle θ zero) and the addressing means 27 do not apply any actuating voltage on the electrodes 20, 21 of these actuators 19. The actuators 19 do not are not addressed. We can refer to Figure 4C. There is no attraction between the moving electrode 21 and the fixed electrode 20 of one of the actuators 19. The electrodes 20, 21 of the actuators 19 are detached and the moving part 10 in the rest position.

When the addressing means 27 begin to apply a first addressing signal, namely an actuating voltage V1 between the two fixed and movable electrodes 20 of one of the actuators 19 (or several actuators located in the same position). side of the axis 12) placed on the right in the figures illustrating this example of operation, nothing happens before the voltage V1 has reached the threshold voltage Vc attraction. At this moment the free end 21.1 of the moving electrode 21 is pressed against the fixed electrode 20 which faces it. This causes the two electrodes to stick together by their ends. The actuator 19 urges the drive arm 23 to the right. In this state, the mobile part 10 and therefore the reflective or refractive zone 17 has turned abruptly by an angle θ greater than + θmin (+ θmin represents the minimum angle of inclination taken by the mobile part 10 with respect to its position of rest). The edge of the movable portion 10 being on the same side of the axis (that is to say the torsion arm 13) that the movable electrode 21 which is pressed against the fixed electrode 20, is lowered and the opposite edge rises.

By increasing the operating voltage V1, the movable electrode 21 is more and more plate on the fixed electrode 20. There is propagation of the plating towards the drive arm 23. The plating surface is close to the arm 23. The movable part 10 inclines more and more until reaching an angle + θmax which corresponds, in a favorable case, to a position in which the entire movable electrode 21 is pressed onto the fixed electrode. 20 if the movable portion 10 does not strike before the bottom of the recess 26. The angle θmax corresponds in the best case to the angle taken by the moving part when the addressing means apply the maximum addressing voltage. As explained above, when the actuating voltage V1 decreases, the moving part 10 adopts the same behavior as before but in opposite direction, the movable electrode 21 gradually separates from the fixed electrode 20. When the operating voltage V1 reaches the threshold voltage Vd detachment, only the end 21.1 of the movable electrode 21 remains plated on the fixed electrode 20. The angle θ decreases. It is when this voltage Vd is applied that the mobile part 10 takes the position + θmin. This voltage Vd is lower than the voltage Vc. When the voltage decreases below Vd, the movable electrode 21 is detached from the fixed electrode 20 and the movable portion 10 resumes its substantially horizontal rest position. The actuating voltage V1 is then canceled.

When the addressing means 27 apply a second addressing signal to actuate the and / or other actuators 19 located on the other side of the axis 12 (left in the figures) namely a V2 actuating voltage (not shown) the movable portion 10 tilts in the opposite direction. The inclination is made from an angle θ greater than -θmin to an angle -θmax plus the actuating voltage V2 is increased. Conversely, when the actuation voltage V2 is decreased, the inclination angle θ decreases until it reaches -θmin.

With such a mode of operation, the mobile part 10 can then move in rotation in two ranges of angles [-θmax, -θmin] and [+ θmin, + θmax] disjoint and / or take a fixed position in these beaches. On the other hand, the range of angles [-θmin, + θmin] can not be explored. It is not possible to obtain a continuous scan of the mobile part 10 in the range of angles [-θmin, + θmin]. This last beach is not exploitable for the mobile part 10. In this operating mode V1 and V2 are never different from zero together. For an actuation voltage that is not zero but less than the threshold attraction voltage Vc, the electrodes of an actuator begin to approach each other, the inclination of the mobile part is small but not zero. It would of course be possible for the addressing means 27 to simultaneously actuate actuators 19 located on either side of the axis 12.

Referring to Figure 7 which shows a second mode of operation of the micro-mirror or the micro-lens according to the invention.

The addressing means 27 now apply a first actuating voltage V1 to the electrodes 20, 21 of one or more actuators 19 located on one side of the axis 12 (in the example on the right) and simultaneously a second voltage V2 actuating the electrodes 20, 21 of one or more actuators 19 located on the other side of the axis 12 (eg left). By suitably choosing the values of these actuating voltages V1, V2, it is possible to make the moving part 10 take all the possible inclinations lying in the angle range [-θmax, + θmax]. By varying these voltages V1 and V2 in time, the mobile part 10 can be animated with a sweeping movement in rotation between -θmax, + θmax.

• V1=V0+V1'
• V2=V0+V2'
• V1'≠0 avec V2'=0 et V2'≠0 et V1'=0.

To facilitate the adjustment of the position or the movement of the mobile part 10, it is possible for the addressing means 27 to permanently apply a non-zero DC voltage V0 to the actuators. this voltage V0 being superimposed on a control voltage V1 'or V2' which can vary in time and which can cancel. The DC voltage V0 is the minimum voltage that maintains the plating of the moving electrode 21 against the fixed electrode 20. It is greater than the breakaway threshold voltage Vd.

• V1 = V0 + V1 '
• V2 = V0 + V2 '
• V1 '≠ 0 with V2' = 0 and V2 '≠ 0 and V1' = 0.

The control voltages V1 'and V2' are never zero at the same time. Suppose we want to rotate the moving part to the right. If V1 'is non-zero, the bonding of the moving electrode propagates to the right and the moving part turns to the right. But if at the same time, V2 'is also non-zero, the collage will also propagate on the left which opposes the rotation of the moving part to the right. The control voltages V1 'and V2' may be indifferently positive or negative.

The addressing means 27 of the actuators 19 may act either at the fixed electrodes 20 or at the mobile electrodes 21 or at the two fixed electrodes 20 and mobile 21 but it is more complicated. Unaddressed electrodes are at ground potential. Since the actuation of the actuators on one side of the axis is independent of that on the other side of the axis, this implies that the fixed or moving electrodes 20 located on one side of the axis 12 electrically isolated from those located on the other side of the axis 12. This insulation can be done conventionally by depositing separate conductive tracks without connection, by isolation trenches, for example air trenches or trenches filled with a dielectric material in conductive zones, by ion implantation of doping zones opposite to that of the substrate in which these zones are implanted.

If it is the fixed electrodes 20 that are addressed, conductive tracks joining them can be made on the base (not shown), under the dielectric layer 24, the mobile electrodes 21 being kept at the same potential (generally the ground potential) .

If the moving electrodes 21 are addressed, all the fixed electrodes 20 can be maintained at the same potential. In this case, the fixed electrodes 20 may be merged and form a single fixed electrode as will be seen later.

In the case where the addressing is done from the fixed electrodes 20, it is possible to break up the fixed electrodes 20 into two distinct portions electrically insulated from each other. The first portion 20.1 corresponding to the part on which the free end 21.1 (or the primer 21.3) of the movable electrode 21 must come to be pressed when it is applied to the DC voltage V0 greater than the threshold voltage of separation Vd as explained previously. It maintains the free end 21.1 of the movable electrode 21 bonded to the fixed electrode 20. The second portion 20.2 corresponding to the portion on which the body 21.2 of the movable electrode 21 must come to be pressed. It is applied to the control voltage V1 'or V2' as it is on one side or the other of the axis 12. This variant is illustrated in Figure 8A. This structure has the advantage, compared with the configuration of FIG. 7, of simplifying the operation of the addressing means 27. It is unnecessary to superimpose the DC voltage V0 on the control voltage V1 'or V2'.

Compared with the examples of FIG. 2, the amplitude of the displacement of the mobile part 10 has been doubled. FIG. 8B represents the response curve (rotation angle θ as a function of the actuating voltages V1 'and V2' applied to the actuators right and left respectively of the micro-mirror or the micro-lens shown in Figure 8. The variation of the inclination angle is linear and continuous between - θmax, + θmax.

In the two examples described, it would of course be possible for the addressing means 27 to simultaneously actuate actuators 19 located on either side of the axis 12, the control voltages V1 'and V2' being non-zero. both at the same time.

Placing the recess 26 under the moving part 10 makes it possible to increase the size of the moving part 10 and consequently the size of the reflective or refractive zone without having to increase the actuating voltage.

Such a micro-mirror or such a micro-lens is particularly well adapted to a use in static or quasi-static mode with a frequency much lower than the mechanical resonance frequency with a large amplitude. However, use in resonant mode is possible if the operating voltages of the actuators are alternating (for example sinusoidal) substantially at the resonance frequency.

We can now refer to Figure 9 which shows a configuration variant for the fixed and movable electrodes 21 of an actuator 19 of a micro-mirror. It could of course be a micro-lens. Instead of the movable electrode 21 having a rectilinear body 21.2 with, if appropriate, a primer 21.3, it is possible for the electrode to be wound on itself substantially in a spiral, the free end 21.1 or the primer 21.3, if it exists, lying substantially in the center of the winding. This variant is illustrated in FIG. 9. The micro-mirror is thus more compact than with rectilinear moving electrodes 21. It would be the same for the micro-lens.

In order to simplify the addressing of the actuators and to improve the compactness of the micro-mirror, it is possible for two or more moving electrodes 21 belonging to actuators 19 located on the same side of the axis 12 to have their end. free 21.1 in common, whether they have a 21.3 primer or not. This variant is shown in Figure 10. It could of course also be a micro-lens. This configuration has the advantage of guarantee a plating exactly the same time 19 corresponding actuators.

An example of a method for producing a micro-mirror or a micro-lens according to the invention will now be described.

It is assumed that the addressing means apply appropriate voltages on the moving electrodes of the actuators to move the moving part in rotation while the fixed electrodes are brought to a constant voltage. (usually the mass). Referring to Figs. 11A-11L. It is assumed that the semiconductor substrates are conductive.

A first substrate 100 is used formed of a base layer 101 of semiconductor material, for example silicon, covered with a sandwich 102 formed by two insulating layers 102.1, 102.2 (for example made of silicon oxide) located on either side of an intermediate layer 102.3 of semiconductor material (for example silicon), the sandwich 102 itself being covered by a surface layer 103 of semiconductor material (for example silicon). This substrate is illustrated in FIG. 11A. The insulating layer referenced 102.1 is the lower layer of the sandwich and the layer 102.2 is the upper layer of the sandwich. Such a substrate 100 may be a double SOI substrate (for Silicon on Insulator). The surface layer 103 is thicker than the intermediate layer 102.3. The layers of semiconductor material 101, 102.3, 103 are conductive.

It is assumed that in this example, the micro-mirror or micro-lens is similar to that of Figures 5A, 5B, the drive and torsion arms are end to end.

First of all, a photolithography step defines the pattern of a first region of the fixed part 14, namely the frame 15.1 or the uprights, of a first region of the mobile part 10, of a first region of the torsion arms. 13 and drive 23. These different elements are then etched in the superficial layer 103 and in the upper insulating layer 102.2 (Figure 11B). This etching step may be a dry etching step. The first regions are thus formed of the semiconductor material of the upper surface layer and the material of the insulating layer. If a micro-mirror is made, the moving part 10 remains full, whereas if a micro-lens is made, the moving part 10 is engraved like a frame with a central recess. This frame engraving is outlined in dotted lines in FIG. 11B.

The moving electrodes of the actuators will be made in the intermediate layer 102.3 later.

The torsion arms, the frame and the moving part will be used to route the addressing signals to the moving electrodes of the actuators. These addressing signals propagate in the frame and the torsion arms from contact pads carried by the frame and made subsequently. One of the torsion arms will be used for the addressing of the actuators located side of the axis and the other torsion arm for addressing the actuators located on the other side of the axis. In order for the addressing signals for the moving electrodes on one side of the axis not to propagate to the moving electrodes on the other side of the axis that they must receive other addressing signals, in the superficial layer 103 and also in the upper insulating layer 102.2 (FIG. 11C), insulating trenches 104 are produced at the frame 15.1 and an isolation trench 106 at the first region of the mobile part 10. These trenches may be air trenches or may be subsequently filled with dielectric material. If instead of having a frame, two amounts are provided as in Figure 4, the latter are electrically isolated by their configuration. The isolation trenches 104 cut the frame 15.1 in two parts 105.1, 105.2, one 105.1 having to bear one of the contact pads transmitting one of the addressing signals and the other part 105.2 to carry the other transmitting contact pad the other addressing signal. The pads are not visible at this stage (FIG. 11C). In the same way, the surface layer 103 corresponding to the first region of the movable part 10 is separated into two parts 107.1, 107.2 by the isolation trench 106. One of the torsion arms originates from one of the parts 107.1 and the other of the other part 107.2. The isolation trench 106 is directed in its majority along the axis of rotation 12. The isolation trench 106 is visible in FIG. 11C.

In a second semiconductor substrate 200 (for example made of silicon) which will act as a second region of the fixed part 14, namely the base 16, a first recessed portion 201 is etched, which will contribute to forming the space Between fixed and movable electrodes actuators and possibly a second recessed portion 202 which will form the recess 26 to be located under the movable portion 10. The first recessed portion 201 is shallower than the second recessed portion 202.

The second recessed portion 202 is located in a central zone of the first recessed portion 201. This etching may be a dry etching. The second substrate 200 thus etched will materialize the fixed electrodes 20 which are then combined for all the actuators. The fixed electrodes are thus included in the base. The second substrate 200 thus etched is then covered with a layer of insulating material 203, for example silicon nitride or an oxide (FIG. 11D). The layer of insulating material 203 materializes the insulating layer 24 inserted between fixed and movable electrodes 20.

The two substrates 100, 200 are then fixed together by placing the first recessed portion 201 opposite the etched surface layer 103 (FIG. 11E). This fixation can be done by a method of molecular adhesion after preparing the surfaces to be assembled in a suitable manner. Such a method of molecular adhesion is known by the acronym SDB abbreviation Anglo-Saxon Silicon Direct Bonding. The second recessed part 202 is opposite with the first region of the movable part 10.

For example, the base layer 101 and the lower insulation layer 102.1 of the sandwich 102 of the first substrate 100 (FIG. 11F) are removed by, for example, rough mechanical rectification followed by wet etching of the silicon.

The intermediate layer 102.3 and the upper insulating layer 102.2 will then be etched to access the surface layer 103 so as to delimit contact pads. The zones thus etched are referenced 108 in FIG. 11G. Ground holes 103 are also etched in the superficial layer 103, which will be used, once metallized, to make resumptions of contact between the moving electrodes and the parts 107.1 and w1.07.1 of the first region of the moving part. 10. These vias 109 are dug in the torsion arms 13 in an area where they project from the movable portion 10 but other locations would be possible. There are as many interconnection holes 109 as mobile electrodes 21. The contact resets will make it possible to electrically connect said parts 107.1, 107.2 to the movable electrodes 21. This etching step is illustrated in FIGS. 11G and 11H.

Then, metal is deposited so as to make the contact pads 110 and the contact resets 111 in the etched areas 108 and the vias 109 (Figure 111). The deposited material may be tungsten, aluminum or any other metal or alloy conventionally used.

FIGS. 11J and 11K show, in section and in plan view respectively, the result of an etching step in the intermediate layer 102.3 which aims to delimit the contour of the moving electrodes 21 with their primers 21.3 and their bodies 21.2, a second region of the movable portion 10, a second region of the torsion arms and drive arms (which are merged). The second region of the moving part, the second region of the torsion arms, the second region of the driving arms are thus formed in the semiconductor material of the intermediate layer 102.3.

The first and second regions of the movable portion, torsion arms and drive arms are superimposed and thus form a stack of the surface layer of the upper insulating layer and the intermediate layer. Of course, an isolation trench 112 is provided between two mobile electrodes located on either side of the axis 12 and which are integral with the same torsion arm 13 and an isolation trench 113 between the mobile part 10 and the moving electrodes 21.

Figure 11L is a section of the micro-mirror or micro-lens in a plane AA of Figure 11J. With reference to FIG. 11C, there are the contact pads 110 and the contact pickups 111.

The reflecting zone 17 of the micro-mirror may be made by the semiconductor material of the intermediate layer 102.3 located at the second region of the mobile part 10 if it has sufficient reflectivity. We could of course metallizing for example gold, silver, aluminum or other of said second region of the movable part.

With regard to the micro-lens, it is possible to relate, for example by gluing, a lenticular refractive pellet 17 to the frame forming the mobile part 10. It is assumed that this pellet is sketched in FIG. 11K. Area 17 could also represent the reflecting zone of the micro-mirror.

The terms "left", "right", "up", "down", "lower", "upper", "horizontal", "vertical" and others are applicable to the embodiments shown and described in connection with the figures. They are used solely for the purposes of the description and do not necessarily apply to the position taken by the micro-mirror when in operation.

Other embodiments of micro-mirrors are conceivable. In particular the number of actuators is not limited to two or four as illustrated. This number can be arbitrary, there is at least one actuator on one side of the axis and at least one actuator on the other side.

REFERENCES CITED:

1. [1] " Two-phase actuators: stable zipping devices without manufacturing of curved structures ", JR Gilbert, SD Senturia, Solid State Sensor and Actuator Workshop, June 1996, Hilton Head SC pages 98-100 .
2. [2] "A Micromachined Deformable Mirror for Adaptive Optics", W. Schwartz, C. Divoux, J. Margail, L. Jocou, Charton J., Stadler E., Jager T., Casset F., Enot T., Proceedings of SPIE 2003 , flight. 4985, pages 230-241 .
3. [3] " A scanning micro-mirror with angular comb drive actuation ", PR Patterson, D. Hah, H. Nguyen, H. Toshiyoshi, Chao R., MC Wu, 2002 IEEE, pages 544-547 .

Claims (63)

1. Micro-mirror made up of a moving part (110), with a reflective zone (17), a fixed part (14), a means of connection (13) of the moving part (10) to the fixed part (14), forming an axis of rotation (12) contained in the moving part (10) substantially parallel to a principal plane of the moving part (10) and means of electrical control (18) of the rotation of the moving part (10) about the axis (12), characterized in that the means of electrical control (18) include two or more actuators (19) each formed of a fixed electrode (20) which forms part of the fixed part (14) and a moving electrode (21) possessing a free end (21.1) and an end which is connected to a drive arm (23) which is substantially parallel to the axis (12) and emerging from the moving part (10), with the moving electrode (21) being suitable for adhering progressively to the fixed electrode (20) from its free end (21.1) when an actuation voltage (V1, V2) is applied between the two electrodes (20, 21) of one of the actuators (19), the adhesion occurs over a surface which varies as a function of the voltage applied between the electrodes of the actuator, with the actuators (19) being arranged on either side of the axis (12).
2. Micro-mirror according to claim 1, wherein the means of connection of the moving part (10) to the fixed part (14) are two torsion arms (13) emerging from the moving part (10) whose ends (11) are connected to the fixed part (14).
3. Micro-mirror according to either claim 1 or claim 2, wherein the axis (12) passes through the geometric centre of the moving part (10).
4. Micro-mirror according to either claim 2 or claim 3, wherein, on the same side of the moving part (10) a drive arm (23) is offset in relation to a torsion arm (13).
5. Micro-mirror according to either claim 2 or claim 3, wherein, on the same side of the moving part (10) a drive arm (23) and a torsion arm (13) are an extension of each other.
6. Micro-mirror according to claim 5, wherein the torsion arm (13) has a transverse section that is less than that of the drive arm (23).
7. Micro-mirror according to claim 5, wherein the torsion arm (13) has a transverse section that is substantially equal to that of the drive arm (23).
8. Micro-mirror according to any of claims 1 to 7, wherein several moving electrodes (21) are linked to the same drive arm (23).
9. Micro-mirror according to any of claims 1 to 7, wherein each drive arm (23) is integral with a single moving electrode (21).
10. Micro-mirror according to any of claims 1 to 9, wherein several moving electrodes (21) located on the same side of the axis (12) are linked together at their free end (21.1).
11. Micro-mirror according to any of claims 1 to 10, wherein at least one moving electrode (21) is wound on itself, with its free end (21.1) located in a central area of the winding.
12. Micro-mirror according to any of claims 1 to 10, wherein at least one moving electrode (21) is substantially rectilinear.
13. Micro-mirror according to any of claims 1 to 12, wherein at least one moving electrode (21) includes a body (21.2) of substantially constant width extending by means of a stub (21.3) at its free end (21.1), the width of the stub (21.3) being greater than that of the body (21.2).
14. Micro-mirror according to any of claims 1 to 13, wherein the fixed electrodes (20) of the actuators (19) are combined.
15. Micro-mirror according to any of claims 1 to 14, wherein the fixed part (14) includes a base (16) and columns (15) on which rest the means (13) of connection, with the moving part (10) being suspended above the base (16).
16. Micro-mirror according to claim 15, wherein the base (16) includes a cavity (26) opposite the moving part (10) which is suspended above the cavity (26).
17. Micro-mirror according to any of claims 1 to 16, wherein the fixed electrodes (20) are covered with a dielectric material (24).
18. Micro-mirror according to any of claims 1 to 17, wherein the means of electrical control (18) include an addressing device (27) capable of applying an actuation voltage (V1, V2) to the moving electrodes and/or the fixed electrodes.
19. Micro-mirror according to claim 18, wherein the actuation voltage is a continuous voltage (V0) added to a variable control voltage (V1', V2').
20. Micro-mirror according to claim 18, wherein at least one fixed electrode (20) of an actuator is divided into two portions (20.1, 20.2) one of which is an end portion (20.1), with these two portions (20.1, 20.2) being insulated from each other, with the addressing device (27) being capable of applying a continuous voltage (V0) to the end portion (21.1) and a variable control voltage (V1', V2') to the other portion (20.2).
21. Micro-mirror according to either claim 19 or claim 20, wherein the continuous voltage (V0) is a minimal voltage for maintaining adhesion of the free end (21.1) of the moving electrode (21) of the actuator onto the fixed electrode (20).
22. Micro-mirror according to any of claims 19 to 21, wherein when the control voltage applied to an actuator located on one side of the axis is non-zero, the control voltage applied at the same time to an actuator located on the other side of the axis is zero.
23. Process for the manufacture of a micro-mirror according to claims 1 to 22, wherein it includes the following steps:

    a) etching of the outline of a first region of the moving part (1), of a first region of the fixed part (14), a first region of the drive arms (23) and of a first region of the means (13) of connection in a surface layer (103) and a first insulating layer (102.2) of a stratified substrate (100) made up of an alternating stacking of a first and second layer (102.1, 102.2) of insulating material and two semi-conductive layers (103, 102.3) one of which is intermediate (102.3) and the other of which is a surface layer (103).

    b) in a second semi-conductive substrate (200) the etching of a recessed part (201), with this second substrate (200) contributing to the formation of a second region of the fixed part (14) and the fixed electrodes (20) of the actuators (19),

    c) assembly of two substrates (100, 200) with the recessed part (201) facing the etched surface layer,

    d) etching of the outline of the moving electrodes (21), of a second region of the moving part (10), a second region of the means of connection (13) and of a second region of the drive arms (23), in the intermediate layer (102.3) and prior metallization (110,111) electrically connected to moving electrodes (21) for the application of the actuation voltage (V1, V2) of each actuator (19) via the fixed part (14) and the moving part (10).
24. Process according to claim 23, wherein trenches of insulation (104, 105) are made during step a) in the surface layer (103) and in the upper insulation layer (102.2) at the first region of the fixed part (10) and the first region of the moving part (14) and in the intermediate layer (102.3) during step d) at the moving electrodes (21) and the second region of the moving part (10) to provide electrical insulation of the moving electrodes (21) during the application of actuation voltage to a moving electrode (21) via the first region of the fixed part (14) and the first region of the moving part (10).
25. Process according to either claim 23 or claim 24, wherein step b) includes the etching of the cavity (26) in a central part of the recessed part (201).
26. Process according to any of claims 23 to 25, wherein step b) is followed by a step for the creation of a layer of insulating material (203) on the second etched substrate (200).
27. Process according to any of claims 23 to 26, wherein the second region of the moving part (10) forms the reflective zone (17).
28. Process according to any of claims 23 to 26, wherein it includes a step for metallization of the second region of the moving part (10) in order to form the reflective zone (17).
29. Process according to any of claims 23 to 28, wherein, after assembly, the second insulating layer (102.2) is removed.
30. Process according to any of claims 23 to 29, wherein the surface layer (103) is thicker than the intermediate layer (102.3).
31. Process according to any of claims 23 to 30, wherein the first substrate is a double SOI substrate and includes next to the second insulating layer (102.2) a semi-conductive base layer (101) which is removed after assembly of the two substrates (100, 200).
32. Micro-lens made up of a moving part (10), with a refringent zone (17), a fixed part (14) a means of connection (13) of the moving part (10) to the fixed part (14), forming an axis of rotation (12) contained in the moving part (10) substantially parallel to a principal plane of the moving part (10), and means of electrical control (18) of the rotation of the moving part (10) about the axis (12) characterized in that the means of electrical control (18) include two or more actuators (19) each formed of a fixed electrode (20) which forms part of the fixed part (14) and a moving electrode (21) possessing a free end (21.1) and an end which is connected to a drive arm (23) which is substantially parallel to the axis (12) and emerging from the moving part (10), with the moving electrode (21) being suitable for adhering progressively to the fixed electrode (20) from its free end (21.1) when an actuation voltage (V1, V2) is applied between the two electrodes (20, 21) of one of the actuators (19), the adhesion occuring over a surface which varies as a function of the voltage applied between the electrodes of the actuator, with the actuators (19) being arranged on either side of the axis (12).
33. Micro-lens according to claim 32, wherein the means of connection of the moving part (10) to the fixed part (14) are two torsion arms (13) emerging from the moving part (10) whose ends (11) are connected to the fixed part (14).
34. Micro-lens according to either claim 32 or claim 33, wherein the axis (12) passes through the geometric centre of the moving part (10).
35. Micro-lens according to either claim 33 or claim 34, wherein, on the same side of the moving part (10) a drive arm (23) is offset in relation to a torsion arm (13).
36. Micro-lens according to either claim 33 or claim 34, wherein, on the same side of the moving part (10) a drive arm (23) and a torsion arm (13) form an extension of each other.
37. Micro-lens according to claim 36, wherein the torsion arm (13) has a transverse section that is less than that of the drive arm (23).
38. Micro-lens according to claim 36, wherein the torsion arm (13) has a transverse section that is substantially equal to that of the drive arm (23).
39. Micro-lens according to any of claims 32 to 38, wherein several moving electrodes (21) are linked to the same drive arm (23).
40. Micro-lens according to any of claims 32 to 38, wherein each drive arm (23) is integral with a single moving electrode (21).
41. Micro-lens according to any of claims 32 to 40, wherein several moving electrodes (21) located on the same side of the axis (12) are linked together at their free end (21.1).
42. Micro-lens according to any of claims 32 to 41, wherein at least one moving electrode (21) is wound on itself, with its free end (21.1) located in a central area of the winding.
43. Micro-lens according to any of claims 32 to 41, wherein at least one moving electrode (21) is substantially rectilinear.
44. Micro-lens according to any of claims 32 to 43, wherein at least one moving electrode (21) includes a body (21.2) of substantially constant width extending by means of a stub (21.3) at its free end (21.1), the width of the stub (21.3) being greater than that of the body (21.2).
45. Micro-lens according to any of claims 32 to 44, wherein the fixed electrodes (20) of the actuators (19) are combined.
46. Micro-lens according to any of claims 32 to 45, wherein the fixed part (14) includes a base (16) and columns (15) on which the means (13) of connection (13) rest, with the moving part (10) being suspended above the base (16).
47. Micro-lens according to claim 46, wherein the base (16) includes a cavity (26) opposite the moving part (10) which is suspended above the cavity (26).
48. Micro-lens according to any of claims 32 to 47, wherein the fixed electrodes (20) are covered with a dielectric material (24).
49. Micro-lens according to any of claims 32 to 48, wherein the means of electrical control (18) include an addressing device (27) capable of applying an actuation voltage (V1, V2) to the moving electrodes and/or the fixed electrodes.
50. Micro-lens according to claim 49, wherein the actuation voltage is a continuous voltage (V0) added to a variable control voltage (V1', V2').
51. Micro-lens according to claim 49, wherein at least one fixed electrode (20) of an actuator is divided into two portions (20.1, 20.2) one of which is an end portion (20.1), with these two portions (20.1, 20.2) being insulated from each other, with the addressing device (27) being capable of applying a continuous voltage (V0) to the end portion (21.1) and a variable control voltage (V1', V2') to the other portion (20.2).
52. Micro-lens according to either claim 50 or claim 51, wherein the continuous voltage (V0) is a minimal voltage for maintaining adhesion of the fee end (21.1) of the moving electrode (21) of the actuator onto the fixed electrode (20).
53. Micro-lens according to any of claims 50 to 52, wherein, when the control voltage applied to an actuator located on one side of the axis is non-zero, the control voltage applied at the same time to an actuator located on the other side of the axis is zero.
54. Process for the manufacture of a micro-lens as described in any of claims 32 to 53, wherein it includes the following steps:

    a) etching of the outline of a first region of the moving part (10), of a first region of the fixed part (14), of a first region of the drive arms (23) and of a first region of the means (13) of connection in a surface layer (103) and a first insulating layer (102.2) of a stratified substrate (100) made up of an alternating stacking of a first and second layer (102.1, 102.2) of insulating material and two semi-conductive layers (103, 102.3) one of which is intermediate (102.3) and the other of which is a surface layer (103),

    b) in a second semi-conductive substrate (200) the etching of a recessed part (201), with this second substrate (200) helping to form a second region of the fixed part (14) and the fixed electrodes (20) of the actuators (19),

    c) assembly of two substrates (100, 200) with the recessed part (201) facing the etched surface layer,

    d) etching of the outline of the moving electrodes (21), of a second region of the moving part (10), a second region of the means of connection (13) and of a second region of the drive arms (23), in the intermediate layer (102.3) and prior metallization (110,111) electrically connected to moving electrodes (21) for the application of the actuation voltage (V1, V2) of each actuator (19) via the fixed part (14) and the moving part (10).
55. Process according to claim 54, wherein trenches of insulation (104, 105) are made during step a) in the surface layer (103) and in the upper insulation layer (102.2) at the first region of the fixed part (10) and the first region of the moving part (14) and in the intermediate layer (102.3) during step d) at the moving electrodes (21) and of the second region of the moving part (10) to provide electrical insulation of the moving electrodes (21) during the application of actuation voltage to a moving electrode (21) via the first region of the fixed part (14) and the first region of the moving part (10).
56. Process according to either claim 54 or claim 55, wherein step b) includes the etching of the means forming the pivot (30.1) in the recessed part (201).
57. Process according to any of claims 54 to 56, wherein step b) includes the etching of the cavity (26) in a central part of the recessed part (201).
58. Process according to any of claims 54 to 57, wherein step b) is followed by a step for the creation of a layer of insulating material (203) on the second etched substrate (200).
59. Process according to any of claims 54 to 58, wherein the moving part (10) is etched in the form of a frame during step b).
60. Process according to claim 59, wherein it includes a step for assembly of a lenticular refringent element to the frame of the moving part in order to form the refringent zone (17).
61. Process according to any of claims 54 to 60, wherein, after assembly in step c), the second insulating layer (102.2) is removed.
62. Process according to any of claims 54 to 61, wherein the surface layer (103) is thicker than the intermediate layer (102.3).
63. Process according to any of claims 54 to 62, wherein the first substrate (100) is a double SOI substrate and includes next to the second insulating layer (102.2) a semi-conductive base layer (101) which is removed after assembly of the two substrates (100, 200).

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